ence graduated into equal spaces, to serve
in measuring revolutions of the end of the wire, to the top of the
bench. Put the bolt in the hole, screwing it through the nut,

[Illustration: Micrometer]

and the construction is complete. The base is improved for the
measuring work by fastening a small piece of wood on the board
between the legs of the bench. A small piece of metal is glued on
this piece of wood at the point where the bolt meets it.

Find the number of threads of the screw to the inch by placing the
bolt on a measuring rule, and counting the threads in an inch of
its length. The bolt in making one revolution will descend a
distance equal to the distance between the threads.

The device is used by placing the object whose thickness is to be
measured on the base under the bolt, and screwing the bolt down
until its end just touches the object, then removing the object,
and screwing the bolt down until its end just touches the base,
carefully noting while doing so the distance that the end of the
wire moves over the scale. The part of a rotation of the bolt, or
the number of rotations with any additional parts of a rotation
added, divided by the number of threads to the inch, will be the
thickness of the object. Quite accurate measurements may be made
with this instrument, says the Scientific American, and in the
absence of the expensive micrometer, it serves a very useful
purpose.

** Another Electric Lamp Experiment [131]

Break a portion of the end off from a 16-cp. globe that has been
thrown away as useless. Shake the globe until all the filament is
broken away, leaving only the ends of the platinum wire exposed.
Screw the globe into a socket that sets upright and fill it with
salt water. Make one connection to the socket from the positive
wire of a 110 volt circuit and the other to a ground. When the
current is turned on small stars will be seen in the globe, which
show up fine at night.
--Contributed by Lindsay McMillan, Santa Maria, Oal.

** Removing Ink Stains [131]

Two or three applications of milk which are wiped up with a dry
cloth will remove india ink spots on carpets.

** Feat of Balancing on Chairs [131]

[Illustration: For Boys Balanacing]

Among the numerous physical exercises is the feat of balancing on
the two rear legs of a chair while one foot rests on the front
part of the seat and the other on the back of the chair. This may
appear to be a hard thing to do, ye